It is known to mount semiconductor electric power control devices, such as FET's, on temperature resistant P.C. boards, for example of temperature resistant ceramic material, wherein the main current carrying electrodes of the semiconductor device are electrically connected, as by soldering, to conventional conductive foils bonded onto the ceramic core of the P.C. board and wherein the semiconductor devices are mounted directly on the P.C. board.
An example of such a structure is a four channel transistor pack (MOD. 200A) manufactured by Siliconix Inc., Santa Clara, Calif.
However, the present Applicant has observed that relatively high electric power and current is handled by the semiconductor devices which energize the tool driving motor of a surgical handpiece, and that as a result, such semiconductor power control devices may get excessively hot, thereby reducing the reliability and operating life thereof.
Further, the present Applicant has observed that the electric power control units of powered surgical handpieces operate in an adverse environment in which liquids and vapors (for example patient body liquids and irrigation liquids present at the operating site) or steam from the sterilization process may, if allowed to come in contact with the power control devices and electric connections thereto, interfere with proper operation of the surgical tool.
Applicant has further observed that it would be desirable to both dissipate (e.g. sink) the excessive heat generated by the power control devices during motor operation and hermetically seal the power control devices and their electrode connections while maintaining the power control package as compact as possible so as to fit within a relatively compact surgical handpiece housing. However, the need for compactness, hermetic sealing and heat dissipation are in conflict with each other and, as far as the present Applicant is aware, no satisfactory solution has been available up to this time. The present invention has resulted from an attempt to meet these conflicting requirements.
Accordingly, the objects and purposes of the present invention include provision of a powered surgical handpiece and an electric power control package therefore in which the electric power control devices for energizing the handpiece motor are compactly housed, provided with effective heat sinking to limit the operating temperature thereof and are enclosed in a hermetically sealed housing to prevent intrusive liquid or vapor contact therewith.
Further objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings.